Typical hydrocarbon fuels, boiling in the gasoline range and intended for the use in spark-ignition internal combustion engines which power most automotive units, contain components which possess limited volatility or solubility in the fuels. In practice such components tend to form deposits in the fuel carburetion system where fuel vaporization occurs. Deposit accumulations on carburetor throttle bodies and plates and intake valves lead to progressively poorer engine performance. Poor performance is exhibited to the operator most noticeably as improper or rough idling of the engine. Less noticeable by the operator is the excessive consumption of fuel and, least of all, the increased level of hydrocarbons and partially burned fuel components in the exhaust gas. Means for preventing or eliminating deposits in carburetor and intake valve systems thus contribute significantly not only to automotive efficiency and economy of operation but also to minimizing pollution of the environment.
Accumulated deposits may be removed periodically by physical cleaning during engine overhaul or tune-up. A preferred solution to the deposits problem requires no interruption of engine usage and this is usually accomplished in practice by inclusion of a carburetor detergent additive in the gasoline fuel. Detergents employed for this purpose are not completely effective but have reduced the severity of the problem.
There is a continuing need for an agent possessing detergency properties such that carburetor deposits may be completely eliminated. The importance of this need is now emphasized by the widespread awareness of pollution problems and the desire to minimize the emission of pollutants from automotive exhaust systems.
Carburetor detergent additives must be soluble in the hydrocarbon fuel composition and possess a suitable balance of lyophilic and hydrophilic properties. Carburetor detergents of the art, while generally alleviating the deposits problem, have exhibited hydrophilic surface-active properties to such a degree that water suspension (haze) and dispersion (emulsion) occur. There continues to be a need for a suitable carburetor detergent additive for automotive systems effective in removing and preventing deposits on carburetor surfaces while exhibiting no undesirable effects upon other properties of the gasoline boiling range hydrocarbon fuel.
New designs for automotive power units make provision for recycle of gases which contain some partially oxidized hydrocarbons having a tendency for form deposits at or near the intake valves. Accordingly, suitable detergent additives for use in automotive fuels must be capable of keeping intake valves clean. There is a need for a suitable intake valve detergent additive for automotive systems effective in removing and preventing deposits in the intake system while exhibiting no undesirable effects upon other properties of the hydrocarbon fuel. Desirably a suitable detergent additive for use in gasoline range hydrocarbon fuel will provide and maintain a high degree of cleanliness in both carburetor and intake systems.
One effective polar grouping suitable for inclusion in oil-soluble surface-active agents is the basic amine grouping, most often as a polyamine and preferably as a polyalkylene polyamine. One suitable non-polar grouping for such agents is the alkaryl group usually provided by alkylation of benzene, naphthalene, phenol or homologs thereof. Such polar and non-polar groups may be conveniently brought together in one molecular by the well-known Mannich condensation reaction involving an alkyl phenol, a low moleular weight aldehyde and a polyamine.
Mannich condensation reactions usually proceed with the formation of polymeric resinous products, either by linear growth due to the use of mono-substituted phenols, by polysubstitution on primary amine groups, or by substitution on secondary amine groups of the polyamine. Cross-linking is also possible when an unsubstituted phenol or naphthol is used or when the condensation reaction is forced by the use of catalysts, high reaction temperature, or both. Excess aldehyde may also react with amine groups to form imines or hydroxymethylamines. Accordingly, the properties of such polymeric compositions have principally been utilized in heavier fuels such as heater and furnace oils, as described in U.S. Pat. No. 2,962,442, and in lubricating oils, as disclosed in U.S. Pat. Nos. 3,036,003 and 3,539,633. None of these uses involves a sensitive carburetion system as is found in the gasoline-powered spark-ignition internal combustion system.
Polymeric Mannich condensation products have often been employed as stabilizers, or anti-oxidants, as well as dispersants, or detergents, in heavy hydrocarbon stocks. Use in lighter hydrocarbon stocks such as gasolines, has been discloed in U.S. Pat. Nos. 3,269,810 and 3,649,229.
U.S. Pat. No. 3,235,484 (Now U.S. Pat. No. Re. 26,330) describes the addition of certain disclosed compositions to refinery hydrocarbon fuel stocks for the purpose of inhibiting the accumulation of carbonaceous deposits in refinery cracking units. The primary inhibitors disclosed are mixtures of amides, imides and amine salts formed by reacting an ethylene polyamine with hydrocarbon substituted succinic acids or anhydride, whose hydrocarbon substituent has at least about 50 carbon atoms. As an adjunct for such primary carbonaceous deposit inhibitors there is disclosed in said patent Mannich condensation products formed by reacting (1) alkylphenol, (2) an amine and (3) formaldehyde in the ratio of one mole alkylphenol and from 0.1-10 mole each of formaldehyde and amine reactant.
U.S. Pat. No. 3,368,972 describes as dispersant-detergent addition agents for lubricating oils high molecular weight Mannich condensation products from (1) high molecular weight alkyl-substituted hydroxyaromatic compounds whose alkyl-substituent has a molecular weight in the range of 600-3000, (2) a compound containing at least one HN&lt; group and (3) an aldehyde in the respective molar ratio of 1.0:0.1-10:1.0-10.
The high molecular weight Mannich condensation products of either U.S. Pat. No. 3,235,484 or U.S. Pat. No. 3,368,972 have a drawback in their large-scale preparation and in their extended service used as lubricant addition agents used under high temperature conditions such as encountered in diesel engines. In the large-scale or plant preparation of such high molecular weight condensation products, especially in light mineral oil solvents, the resulting oil concentrate solution of the condensation product either has or develops during storage a haze which is believed to be caused by undissolved or border-line soluble by-products which not only are not substantially incapable of removal by filtration but also severely resrict product filtration rate. When used in diesel engine crankcase lubricant oils and subject to high temperature in service use, piston ring groove carbonaceous deposits and skirt varnish tend to build up sufficiently rapidly and prevent desirable long in-service use of such lubricant oils.
Various olefin polymers have been added to hydrocarbon fuels ranging from gasolines to diesel fuels to heavy oil fractions. Petrolatums have also been employed in gasolines. One recent example of such use of certain olefin polymers is described in U.S. Pat. No. 3,502,451, where gasoline motor fuel is claimed to be improved in its ability to maintain cleanliness of intake valves and parts.